The present invention relates to a drive system having a wide width structure integrally assembled with a feed screw and a linear guide device, for example.
There is known a drive system having a structure provided with a feed screw as driving means such as ball screw, slide screw or like and a linear guide device. Such drive system essentially comprises a screw shaft formed, at its outer surface, with a spiral groove, a linear guide rail as longitudinal track table arranged in parallel to the screw shaft and a block as movable member assembled with the linear guide rail to be movable along the longitudinal direction thereof, and this movable block is provided with a nut member to be screwed with the screw shaft.
Further, in general, a machine tool, a machine table or like is operatively mounted to such drive system and moved to a desired position and stopped there. This positional control of the machine tool, for example, is performed by controlling the rotational motion of the screw shaft through the operation of a motor or like drive means. As mentioned above, such drive system may be said as a compact feed unit having a good assembling performance and adjustment, and accordingly, has been utilized for various industrial robots, conveying equipments and the like.
For example, as shown in Japanese Utility Model Laid-open Publication No. HEI 2-12554, the drive systems of the type mentioned above generally includes the following two types, one being a straddle-type in which a movable table, having a bottom portion and lateral side portions extending in the longitudinal direction thereof, is straddled on the track table to be movable therealong and the other one being an idly groove-fitting type in which a movable member having a rectangular section is idly fitted into a recessed groove of a track member having box-shaped section to be movable in the longitudinal direction thereof.
In the case where both the above two types are compared with each other at the same rated load, a linear guide device utilizing the idly groove-fitting type can be formed to have a height lower than that of the straddle type, and hence, can be made compact, thus being arranged in a small space. In this meaning, it may be said that the idly groove-fitting type structure is effectively utilized for robots or conveying units which are likely to be used with restricted or reduced space.
The idly groove-fitting type structure will be described more in detail hereunder with reference to FIGS. 7 and 8.
A track table 90 having box-shaped section and having longitudinal extension is composed of a horizontally flat portion as a bottom portion 90a and a pair of lateral side portions standing upward from the bottom portion 90a as viewed in FIG. 7 or 8 so as to form a recessed portion therebetween. The lateral side portions are formed with inner side surfaces 91, 91 to which two rows of upper and lower ball rolling grooves 92, 92 are respectively formed so as to extend in the longitudinal direction in parallel to each other. Further, a screw shaft 93 for the ball screw is arranged in the lateral central portion of the box-shaped track table 90 to be parallel to the ball rolling surfaces 92, 92.
A movable table 94 is a member having a top surface on which a table T or like is mounted to convey a machine tool or like tool, or other articles disposed on the table T. The movable table 94 has a rectangular section and is formed with a nut portion (member) 95 so as to be screwed with the screw shaft 93. The movable table 94 has a width dimension slightly smaller than an inner width dimension of the recessed portion of the track table 90 as can be seen from FIG. 8.
The movable table 94 is hence idly fitted to the recessed portion (groove) of the track table 90. The movable table 94 is formed with lateral side surfaces to which loaded ball rolling surfaces 94a, 94a are formed so as to be opposed respectively to the ball rolling grooves 92, 92 formed to the inside surfaces 91, 91 of the track table 90. Furthermore, ball return passages, each composed of a linear through hole, are formed in a solid portion of the movable table so as to extend in parallel to the loaded ball rolling surfaces 94a, and U-shaped rolling direction changing passages are also formed to the movable table at both longitudinal end portions thereof so as to communicate the loaded ball rolling surfaces 94a with the ball return passages 94b, respectively, thereby constituting an endless ball circulation passage in which a number of balls 97 as rolling members circulate while rolling therealong.
In the operation, when the screw shaft 93 is rotated through the driving of a servo-motor, not shown, the movable table 94 is moved in association with the rotational motion of the screw shaft 93 and guided along the track table 90 in its longitudinal direction. In this operation, the movement of the movable table 94 can be smoothly performed through the rolling motions of steel balls B arranged between the nut member 95 and the screw shaft 93 and the balls 97 arranged between the track table 90 and the movable table 94. Further, a load of an article such as machine tool, table or like article applied to the movable table 94 through the table T on which the article is mounted to be conveyed is directly applied to a number of balls 97 arranged and rolling between the ball rolling surfaces 92, 92 and the loaded ball rolling surfaces 94a, 94a. Furthermore, the ball rolling surfaces 92, the loaded ball rolling surfaces 94a and the balls 97 are arranged so as to make minus the gaps, in dimension, between each of the ball rolling surfaces 92 and each of the balls 97 and between each of the loaded ball rolling surfaces 94a and each of the balls 97 to thereby apply a preload to the balls 97.
However, in a conventional drive system in which the structure mentioned above is simply applied to a drive system having a wide width structure, the bottom portion 90a of the track table 90 having a wide width dimension is likely deformed or bent by a moment load Mc (FIG. 8) in a rolling direction applied to the movable table 94, thereby opening outside the both lateral portions having the inside surfaces 91, 91 to which the ball rolling grooves are formed. As a result, there causes a case where the tight close contact between the ball 97, the ball rolling surface 92 and the loaded ball rolling surface 94a is loosened and it becomes difficult to give a sufficient preload to the ball 97 and a case where the movable table 94 causes a rolling, yawing or pitching motion because of the reduced preload and, hence, a smooth linearly advancing motion cannot be expected, thus being inconvenient.
In order to obviate the defect mentioned above, a prior art has provided one idea that a plurality of such drive systems are arranged side by side in parallel to each other. However, such plural lateral arrangement requires a wide space in the width direction and is not usable for disposing in a narrow limited space. Moreover, such parallel arrangement will require a high performance in the parallel alignment and location working for such requirement and for making minimum an operational resistance also requires much time and labor for an operator, as well as increasing in manufacturing cost for plural drive systems.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a drive system having a wide width structure in which there is less change in preload between a rolling member and a rolling member rolling surface even in a case where a load, particularly, a moment load in the rolling direction, is relatively large, and the dimension in the width direction of the drive system is made compact, and an assembling working can be performed easily and smoothly with reduced manufacturing cost.
This and other objects can be achieved according to the present invention by providing a drive system, particularly having a wide width structure, comprising:
a track table comprising a flat portion, perpendicular side portions extending in parallel to each other along both lateral side edges of the flat portion in a longitudinal direction thereof and at least one partition section formed to the flat portion at a portion between the perpendicular side portions so as to extend in parallel thereto, the perpendicular side portions having inside surfaces to which rolling member rolling surfaces are formed so as to extend in a longitudinal direction thereof and the partition section having both side surfaces to which loaded rolling member rolling surfaces are formed so as to extend in a longitudinal direction thereof;
a plurality of movable tables fitted into a space defined between one of the perpendicular side portions and the partition section or between the partition sections, the movable tables each having lateral side surfaces to which loaded rolling member rolling surfaces constituting rolling member circulation passages are formed respectively so as to correspond to the rolling member rolling surfaces;
a number of rolling members disposed and arranged in the rolling member circulation passages so as to circulate therein in accordance with relative movement between the track table and movable tables; and
a drive means for driving the track table and the movable table so as to cause the relative movement therebetween.
In preferred embodiments or examples, each of the movable table is formed with mount portions for mounting an article to be conveyed, which mount portions are formed on said movable tables at a portion which is substantially central on said movable tables along the moving direction thereof, while being offset toward the side portions of the track table.
The track table is an outer rail and the movable tables are inner blocks.
The driving means comprises a feed screw, a feed screw shaft and a motor means operatively connected to the feed screw shaft. When balls are used as rolling members, the feed screw is a ball screw arranged for each movable table, the feed screw shaft is a ball screw shaft for each ball screw, and a plurality of the ball screw shafts are driven synchronously by at least one motor.
The flat portion, the perpendicular side portions and the partition section of the track table are formed integrally with each other. The track table and the movable tables are formed as a linear guide device in assembly.
According to the structure and subject features of the present invention mentioned above, since the partition section is provided for the track table, the flat (bottom) portion thereof cannot be bent even if it has a wide width dimension and, therefore, the anti-moment-loading ability can be improved and the side portions of the track table are not opened outward. Accordingly, preload applied to the rolling members and rolling member rolling surfaces is hardly changed, thus ensuring the smooth movement of the movable table. Furthermore, since it is not necessary to arrange a plurality of guide devices side by side, the location space in the width direction can be reduced, and assembling or arranging time and labour can be reduced with less cost.
Furthermore, since the mount portions (fastening bolt holes) are disposed to the movable table at a portion which is substantially central on said movable table along the moving direction thereof, while being offset toward the side portions of the track table, the load of the article to be conveyed is applied evenly on the respective perpendicular side portions and partition section, so that the anti-moment-loading abilities to the rolling member rolling surfaces can be made substantially equally, thus providing a balanced rigidity. The movable table can be hence more smoothly moved. The formation of the fastening bolt holes as the mount portions can make a mounting of the article to be conveyed entirely easy and smooth, and meke the entire strucure of the moveable table simple and compact.
The natures and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.